This invention relates to telecommunications systems, particularly submarine cables systems.
Submarine telecommunications systems make great demands on component reliability since a system, once laid, is expected to have a working life in excess of 20 years. Consequently the electronic circuitry associated with the amplifiers and equalizers of such a system must be highly reliable and to this end they are manufactured under conditions of extreme cleanliness. It is important that the amplifying repeater circuitry be designed to be as uncomplicated as possible. For this reason, new electronic techniques and components are considered with extreme caution before making any changes in current practice, again with a view to maintaining high reliability.
In attempts to keep the repeater circuitry as simple as possible, the amplifiers have a fixed gain, that is to say the amplifier gain cannot be altered once the repeater casing is sealed. Provision is made for making last-minute adjustments to equalizers (passive networks) during laying the cable system to adjust for cable attenuation and to allow for predicted changes in the total system attenuation due to seasonal water temperature changes and ageing. For a better understanding of current techniques reference is directed to ITT Electrical Communication Volume 46, No. 2 1971, pages 139 to 156.
As system frequencies become higher, system gain performance may get worse so it is considered most desirable now to be able to remotely adjust some parameter of the system to effect compensation.